Re: UDP & TCP

From: Dusko Savatovic (savatovic.removespam_at_hotmail.com)
Date: 03/10/04 

Date: Wed, 10 Mar 2004 10:53:39 +0100

To display all open ports (TCP and UDP) open cmd prompt and run command:
netstat -ano
To find out which ports are blocked, consult your firewall software. If you
use ICF in WinXP/2003, then only ports that were explicitly opened are
opened, others are blocked. Explicitly opened ports are configured ports
like FTP, Messenger Service, Remote Desktop etc, plus high numbered ports
that are opened when initiating outbound connection. When reply is received
on that port, it is automatically closed and a new one is opened.
If, however, you are not using firewall, then any packet that is received is
forwarded to the corresponding listening service. If listening service does
not exist for that packet (port), the packet is discarded. This may lead to
flooding certain services with malformed packets that may crash the service
and in certain cases can enable attacker to crash service or entire system
or gain complete control of your system.

Dusko Savatovic

"William C." <cmchong20@yahoo.com> wrote in message
news:evBMewnBEHA.624@TK2MSFTNGP10.phx.gbl...
> How to check whether eg. certain UDP or TCP ports are closed or open?
>
>

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